Method of improving filaments of hydrolyzed olefin/vinyl organic ester interpolymers



" of from 90 C. to 100 Patented Nov. 19, 1946 METHOD F HYDROLYZED IMPROVING FILAMEN TS 0F OLEFlN/YINYL ORGANIC ns'rnn rN'rERroLYMERs Halsey B. Stevenson,

assignor to E. I. du P pany, Wilmington, D

ware

No Drawing. Applicati Serial No.

This invention relates to improved hydrolyzed olefin/vinyl organic ester interpolymer, filaments and, more particularly, to a new process for im- I proving the hydrolyzed mers.

This invention has as an of oriented filaments of hydrolyzed ethylene/vinyl properties of filaments derived from a temperature within the range of from 80 C. to 100 C. in a medium containing H2O a filament of a substantially completely hydrolyzed interpolymer of ethylene with a vinyl ester of a monocarboxylic acid having the general formula RCOOH wherein R is of the atoms and hydrocarbon radicals, said acid being 101 C. to 106 0., in a taut condition, with a medium comprising H2O at a temperature within the range of from 101 C. to 106 C.

A preferred embodiment of this invention 'comprises drawing, at a temperature within the range C. in steam at a temperature within the range of from 90 (1110 100 0.,

v a filament of a substantially completely hydrolyzed interpolymer of ethylene with vinyl acetate,

olefin/vinyl organic ester interpolytil are in parts by weight unless Brandywine- Hundred, Del.,

ont de Nemours & Comel.,'a corporation of Delaon October 18, 1944, 559,231

5 Claims. (Cl. .8130.1)

resultant stretched filament in and at a temperature within therange of :from 102 C. to 104 C. within the range of from 102 C. to'104 The following examples, in

otherwise: specified,

I Ewample I L V An interpolymer oi ethylen-e and vinyl acetate having a molar ratio oi 2.6/1 of ethylene to vinyl of ethylene at about 1000 atmospheres pressure and at about C. to vinyl acetate containing a small amount of benzoyl peroxide. The ethylene/vinyl acetate interpolymer' was hydrolyzed in a benzene-methanol solution with excess caustic and the interpolymer was isolated and the elongation and a when immersed for 5 minutes approximately C.

drawn yarn was wound-on a metal slight. tension and heat treated by minutes, the yarn had a tenacity of 4.4' g./d. at 16% elong ,tion and had a shrinkage of only 8.5% when immersed in boiling. water for 5 minutes.

Example If A'melt-spun' yarn of a substantially completely hydrolyzed ethylene/vinyl acetate interpolymer having a molar ratio of ethylene-vinyl acetate of 2.8/1 was drawn in steam at 99-100 g. at a draw ratio of 5.3/1 to give an oriented yarn having a tenacity of 3.7 g./d. at ing a shrinkage of 27% whenvheated in water to 100 C. This yarn was heat about 5 minutes atl0 3 C. When the above yarn was set at 100 C. in steam under otherwise identical conditions, the heat-set yarn had a tenacity of 3.7 g./d. at 20% elongation but had a shrinkage of 13% Jected to water at 100 C.

steam in an autoclave at 104 for 5 which proportions elongation and havtreated in steam for Example III A hydrolyzed ethylene/vinyl-acetate interpolymer of molar ratio of ethylene/vinyl acetate of approximately 2.4/1 was dissolved in a trichloroethylene-ethanol mixture and filaments obtained by dry-spinning" the solution. The yarn was oriented by drawing in steam at 99 C. at a draw ratio of 8.11/1 to give a yarn having a tenacity of 3.9 g./d. at 12% elongation. The yarn was set in steam at 102 C. to give filaments having a tenacity of 3.8 g./d. at 19% elongation. The heat-set yarn had a shrinkage of 12% when treated in water at 100 C. When the unset or untreated yarn to the steam treatment was placed in boiling water, the yarn was so water-sensitive'that it broke.

The process of this invention is applicable to any filament of a hydrolyzed interpolymer of ethylene with a vinyl ester of an organic acid having the general formula RCOOH, wherein R is of the group consisting of hydrogen atoms and hydrocarbon radicals, said acid being free from unsaturated linkages between acyclic'carbon atoms and any carbon atom alpha to the carbon atom in the carboxyl group of said acid being attached to at least one but not more than three carbon atoms, provided the mol ratio of ethylene to vinyl/organic ester in said interpolymer prior to hydrolysis was within the range of from 1/1 to 1. Included among examples of said interpolymers are interpolymers of ethylene with vinyl formate, with vinyl acetate, with vinyl propionate, with vinyl butyrate, with vinyl stearate, with vinyl benzoate, with vinyl cyclohexanoate, with vinyl isobutyrate, with vinyl palmitate, with vinyl myristate, with vinyl toluate, with vinyl naphthoate and the like. On account of superior products had therewith, I prefer to employ interpolymers of ethylene with a vinyl ester of an organic acid having the general CnH2n+1COOH, wherein n is a positive integer within the range of from 1 to 3. Inasmuch as the acid group of hydrolysis, it is usually most economical to use an interpolymer ofethylene with vinyl acetate which is the most readily available vinyl ester.

Appreciable effects are had when the mol ratio of ethylene to vinyl organic ester in the interpolymer prior to hydrolysis is as low as 1/ 1, and also.when it isas high as 5/1. However, the filaments obtained according to the process of this of ethylene to vinyl organic hydrolysis is when the mol ratio ester in said interpolymer prior to within the range of from 2/ 1 to 4/ 1. As indicated in tion of the vinyl ester with ethylene can be carried out under super-atmospheric pressure in the presence of a peroxygen-type polymerization catalyst. The resulting interpolvmei' may be hydrolyzed either in a lower aliphatic alcohol solutreatment with alkali hydroxide. For preparing filaments the. resulting hydrolyzed interpolymer should be-at least 80% hydrolyzed and preferably substantially completely hydrolyzed.

The heat stability and water resistance of the fibers had in accordance with this invention are improved if the hydrolyzed ethylene/vinyl ester interpolymer is subjected to an extraction with hot methanol prior to formation of thefibers.

As shown in the examples, the filaments may be obtained by either melt spinning of the hywhich had not been subjectedtion or aromatic hydrocarbon-alcohol solution by hols boiling above 75,

, 4 drolyzed ethylene/vinyl organic ester interpolymer or byspinning from a solution of the interpolymer with subsequent evaporation of the solvent. Suitable solvents are trichloroethyleneethanolewater mixtures, primary aliphatic alcoe primary and secondary aliphatic amines and mixtures of aromatic hydrocarbons with such alcohols and amines.

As hereinbefore stated, it is essential that the filament should be drawn in a medium comprising water at a temperature within the range of from 80 C. to 100 C. Furthermore, the time of travel of the filament through the drawing medium must be such that said filament is heated to a temperature within said range. While appreciable effects are obtained when'drawing is effected at a temperature as low as 80 C., markedly improved filaments are produced when the temperature of the aqueous medium and the filament during the drawing step is within the range of from 90 C. to 100 C. While the medium comprising H2O in which thedrawing .of the filament is effected may be a bath of liquid water, said drawing is carried out most readily and conveniently and with the production of filament products having optimum properties when said medium comprises steam. The drawing or orientation of the filament as described above is therefore preferably carried out in steam, or steam and air, at a temperature within the range of from 90 Cfto 100C. Drawing can be conveniently effected by passing the filament from the snubbing roll to the drawing roll through a vertical tube open at both. ends and to which steam is admitted. By maintaining a speed difthe tension on the drawing roll being suflicient'to formula the vinyl ester is removed by invention have markedly superior resistance to hot water and substantially improved dye receptivity Example I, interpolymerizabut insufficient to cause break- By passing steam in the verwhich the filament is passed effect stretching ing of the filament. tical tube through during the drawing operation, it may be heated readily to the desired temperature. The use of steam alone usually provides a temperature within the range of from 99 peratures of from C. to 99 C. to 100 C., while tem- C. are attained before it is introduced into the tube. Suchheating prevents local over-heating of the filament and avoids the tendency to form broken filaments. Less-pref erable, although operable, is the employment of a liquid water bath heated to a temperature within the range of from 80 C. to 100 C. The use of such baths necessitates guides for the filamentsand these may bring about breakage of the filaments. Instead of baths of substantially pure liquid water, there may be employed baths of aqueous solutions, e. g., aqueous salt solutionsheated to the desired temperature. However, aqueous baths of substantially pure liquid water provide filaments having higher tenacities than are obtained through the employment of baths of aqueous solutions; while highest tenacities are obtained when the medium employed in the drawing operation 'is steam,

rawing temperatures above 100 C. cannot be used. Below 80 C., the filament is softened insufficiently for good drawing and lower drawing ratios In general the time of travel of'the filament through the drawingmedium is 1 to 5 seconds, although usually .1 to 3 seconds are preferred. The time is related to filament size, drawing medium and drawing temperature. With regardto either substantially pure with lowertenaci- I 'ties (poorer final properties) are obtained.

' oriented, it must be set. about according to the .process of this invention time of travel. the output or a drawing unit depends on the drawing require longer tubes or baths for theheating.

It is to be understood that, duringthe drawing ratio short of the breaking operation, any draw point of the filament may be employed. How-'- ever. on account of the superior products thereby obtained, I prefer to employ draw ratios within the range of from 4.5/1 to 8.5/1, i. e. to draw the filament to a length within the range of from 450% to 850% of its original length.

Best results have speed and high speeds may fixed length or under a slight tension to prevent shrinkage during the operation. In practice, it

is convenient to wind the filament on a'Iheat-resistant bobbin or similar member to maintain said filament at a fixedlength during the setting oporation.

The low shrinkage in boiling water (5% to I 01' the filaments obtained in accordance been obtained by orienting or drawing of the filament which has first been by contacting the drawn filament in taut condition with a medium comprising H2O ata temperature within the range of from 101 C. to 106 C. Although the medium comprising H may I be liquid water at a temperature of from 101 C.

'to 106 0., it is more convenient to use steam.

Furthermore, when said medium is steam, filaments having markedly superior properties result. The heat transfer from steam is better than from liquid Water'and the filament attains the required temperature within the range of from 101 C. to 106 C. more'rapidly and with better control. Equipment adapted for treatment of the filament with steam, e. g., an autoclave, is readily available and..when thefilament is removed from the steam bath it may be dried quick. ly. It is preferred that the time of heat treatment in steam should not exceed 20 minutes since heating times in excess of 20 minutes result in degradation of the filaments. In general, optimum results are had when thefilament is coritacted with steam at from 102 C. to 104 C. for a period of time within the range of from utes to 20 minutes, although when the filament is treated in the form of thick packages of yarn, sumcient time must be allowed to obtain equilibrium temperature throughout the package.

Setting temperatures in excess of 106 C. are to be avoided since such high temperatures usually cause some degradation of the filament with resulting loss of "tenacity and other properties.

On the other hand, when setting temperatures of less than 101 C. are employed, the resultant filament is not shrinkage in boiling water. The subsequent temperature employed within the heat-setting range of from 101 C. to 106 C. may vary with the particular hydrolyzed interpolymer depending upon the molecular weight of said interpolymer and the ratio of ethylene to vinyl organic ester originall'y'present in said interpolymer prior to hydrolysis. The exact setting temperature for maximum properties of any given filament can readily be determined. This determination may be readily carried out by a few preliminary exaerlnients to find the optimum conditions.

The setting or heat treatment in the medium :omprising H2O at a. temperature within the range )1 from 101 C. to 106 0. must be carried out vith the filament in a taut condition, 1. e., at a protected against subsequent] elongation. Said filaments are 5 min drolyzed ethylene/vinyl with this invention as compared to the shrinkage of from 15% to 60% of hydrolyzed ethylcarried out at elevated temperatures. The filaments'as obtained by the process of this invention have improved dye receptivity and increased particularly useful in the production of fabrics such as hosiery. filter cloths, battery separators, tents and the like.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myseli to the specific embodiments thereof except as defined in the appended claims.

Having described the present invention, the following is claimed as new and useful:

1 The process for obtaining an improved hydrolyzed ethylene/vinyl organic ester interpolymer filament, which comprises drawing at a temperature within therange 01 from C. to 100.

C. in a medium containing H2O at a temperature within the range of from 80 C. to 100 C., a filament of a hydrolyzed interpolymerof ethylene with a vinyl ester of a monocarboxylic acid having the-general formula RCOOH, wherein R is of the group consisting 01' hydrogen atoms and, hydrocarbon radicals, said acid being free from unsaturated linkages between acyclic carbon atoms and any carbon atom alpha to the carbon atom in the carbo yl group of said acid being attached to at least one but not more than three carbon atoms, the mo] ratio of ethylene to vinyl organic ester in said interpolymer prior to hydrolysis having been Within the .range of from 1/1 to 5/1, and thereafter heating the resultant stretched filament at a temperature within the range of from 101 C. to 106 C. in a taut condition in contact with a, medium comprising H2O at a temperature within the range 01 from 101 C(to 106 C.

2. The process for obtaining an improved hyorganic ester interpolymer filament, which comprises drawing at a temperature within the range of from C. to C. in a medium comprising H2O at a temperature within the range of from 90 ment of a hydrolyzed interpolymer of ethylene with a vinyl ester of a monocarboxylic acid having the general formula CnHZn-i-ICOOH, wherein n is a positive integer within the range of from 1 to 3, the mol ratio of ethylene to vinyl organic ester in said interpolymer prior to hydrolysis having been within the range of from 1/1 to 5/1,

from 1 to 5 seconds in a medium comprising steam at a temperature within the range of from 90 C. to 100 C., a filament of a substantially completely hydrolyzed interpolymer of ethylene with vinyl,acetate,. the mol ratio of ethylene to vinyl acetate in said interpolymer prior to hydrolysis having been within the range of from 1/1 to 5/1, and thereafter contacting the resultant stretched filament in a taut condition for a period of from 5 to 20 minutes with amedium comprising steam at a temperature within the range of from 101 C. to 106 C.

4. The process for obtaining an improved bydrolyzed ethylene/vinyl acetate interpolymer fila-- ment, which comprises drawing for a period of from 1 to 5 seconds in steam at a temperature within the range of from 90 C. to 100 C., a filament of a substantially completely hydrolyzed interpolymer of ethylene with vinyl acetate; the

' mol ratio of ethylene to vinyl acetate in said interpolymer prior to hydrolysis having been within the range of from 1/1 to 5/1, and thereafter contacting the resultant stretched filament in a taut condition for a period of from 5 to 20 minutes with steam at a temperature within the range of 7 mol ratio of ethylene to vinyl acetate in said interpolymer prior to hydrolysis having been within the range of from 2/1 to 4/1, and thereafter contacting the resultant stretched filament in a taut condition for a period of from 5 to 20 minutes with steam at a temperature within the range of from 102 C. to 104 C.

HALSEY B. STEVENSON. 

